Skin Barrier Function in Psoriasis and Atopic Dermatitis: Transepidermal Water Loss and Temperature as Useful Tools to Assess Disease Severity

Abstract

Multiple diagnostic tools are used to evaluate psoriasis and atopic dermatitis (AD) severity, but most of them are based on subjective components. Transepidermal water loss (TEWL) and temperature are skin barrier function parameters that can be objectively measured and could help clinicians to evaluate disease severity accurately. Thus, the aims of this study are: (1) to compare skin barrier function between healthy skin, psoriatic skin and AD skin; and (2) to assess if skin barrier function parameters could predict disease severity. A cross-sectional study was designed, and epidermal barrier function parameters were measured. The study included 314 participants: 157 healthy individuals, 92 psoriatic patients, and 65 atopic dermatitis patients. TEWL was significantly higher, while stratum corneum hydration (SCH) (8.71 vs. 38.43 vs. 44.39 Arbitrary Units (AU)) was lower at psoriatic plaques than at uninvolved psoriatic skin and healthy controls. Patients with both TEWL > 13.85 g·m^-2h^-1 and temperature > 30.85 °C presented a moderate/severe psoriasis (psoriasis area severity index (PASI) ≥ 7), with a specificity of 76.3%. TEWL (28.68 vs. 13.15 vs. 11.60 g·m^-2 h^-1) and temperature were significantly higher, while SCH (25.20 vs. 40.95 vs. 50.73 AU) was lower at AD eczematous lesions than uninvolved AD skin and healthy controls. Patients with a temperature > 31.75 °C presented a moderate/severe AD (SCORing Atopic Dermatitis (SCORAD) ≥ 37) with a sensitivity of 81.8%. In conclusion, temperature and TEWL values may help clinicians to determine disease severity and select patients who need intensive treatment.

Keywords: atopic dermatitis; homeostasis; psoriasis; skin barrier; transepidermal water loss.

Figure 1

Homeostasis parameters between psoriatic patients and healthy participants and homeostasis parameters between atopic dermatitis patients and healthy participants. (A) Transepidermal Water Loss (TEWL) between psoriatic patients and healthy participants and TEWL between atopic dermatitis patients and healthy participants. (B) Stratum corneum hydration (SCH) between psoriatic patients and healthy participants and SCH between atopic dermatitis patients and healthy participants. (C) Temperature between psoriatic patients and healthy participants and temperature between atopic dermatitis patients and healthy participants. (D) Erythema between psoriatic patients and healthy participants and erythema between atopic dermatitis patients and healthy participants. (E) Elasticity between psoriatic patients and healthy participants and elasticity between atopic dermatitis patients and healthy participants. (F) pH between psoriatic patients and healthy participants and pH between atopic dermatitis patients and healthy participants. Photo caption: AD, atopic dermatitis, AU, arbitrary units, SCH, stratum corneum hydration, TEWL, Transepidermal Water Loss. * p value after using Student’s t test for independent samples to compare homeostasis parameters between healthy skin and uninvolved psoriatic skin. ** p value after using Student’s t test for independent samples to compare homeostasis parameters between healthy skin and psoriatic plaque. *** p value after using Student’s t test for paired samples to compare homeostasis parameters between uninvolved psoriatic skin and psoriatic plaque. ^# p value after using Student’s t test for independent samples to compare homeostasis parameters between healthy skin and uninvolved AD skin. ^## p value after using Student’s t test for independent samples to compare homeostasis parameters between healthy skin and eczematous lesion. ^### p value after using Student’s t test for paired samples to compare homeostasis parameters between AD skin and eczematous lesion.